This section provides background information related to the present disclosure which is not necessarily prior art.
Accessories such as coolant pumps and cooling fans are in common use in modern vehicles that employ an internal combustion engine for the production of propulsive power or the generation of electricity. Such accessories are commonly driven by a belt directly or indirectly attached to the crankshaft of the engine and thus operate at a rotational speed that is related in a fixed manner to the rotational speed of the crankshaft.
It would be desirable to reduce the power that is consumed by such accessories to improve fuel economy and to reduce engine emissions. It would thus be preferable if such accessories could be made to operate with less power, or only when needed, in order to reduce the load on the engine and, in turn, improve fuel economy and reduce undesirable emissions from the engine.